What Oil To Use For A Lawn Mower | 10W-30 vs 5W-30 vs SAE 30

If you’ve just bought a new petrol lawn mower, or your current bottle of oil is about to run out, you might be wondering what’s the best type of oil to buy.

In this guide, we’ve explained what type of engine oil to use for your lawn mower, to help prolong its longevity, and improve performance.

What oil to use for your lawn mower

There are three types of oil that are best to use in a lawn mower.

  • 10W-30: works well at all temperatures, and helps to make cold starts easier. However, oil consumption will be a bit higher.
  • 5W-30: also works well at all temperatures, and has a slightly lower oil consumption.
  • SAE 30: works well in warm temperatures, and is best for older two-stroke engines.

For modern lawn mowers, we’d recommend 10W-30 if you live in a colder part of the UK, such as up north, and sometimes struggle to start your mower in cold weather. However, if you’re more concerned about oil consumption, 5W-30 is also a great choice.

You can also use SAE 30 oil in your lawn mower, if you’d like – it’s quite a common choice, and is cheaper to buy than these other two types of motor oil. And for older two-stroke mowers, SAE 30 is often your only choice.

SAE 30 is an older type of oil that has the same viscosity at hot and cold temperatures, meaning it doesn’t flow very well when it’s very cold. It’s not used in cars anymore – modern motor oils like 10W-30 and 5W-10 are designed to vary their viscosity according to the temperature. The “W” in their name stands for “winter”, and describes the oil’s viscosity in cold climates.

The fact that SAE 30 doesn’t flow very well in cold weather isn’t a big issue for lawn mowers, since you’ll mostly be mowing the lawn in the warmer months of the year. However, we still generally recommend 5W-30 over SAE 30 if you have a four-stroke motor, just in case you ever need to cut the grass when it’s a bit cold outside.

Two-stroke engines are often designed to use older types of oil, such as SAE 30. On the other hand, more modern four-stroke lawn mower engines can perform ever so slightly better with multi-viscosity oils, such as 10W-30. Remember, with a two-stroke motor, you need to mix the petrol and oil before adding it to the mower, rather than adding the two separately.

It’s best to use synthetic oil rather than mineral oil in your lawn mower if possible. Synthetic oils, which are produced using man-made chemical compounds, perform better than mineral oils. They flow better, and last longer – the difference between the two is more noticeable when used in a car, but to get the most from your lawn mower’s oil, it’s best to buy fully synthetic or at least semi-synthetic engine oil if possible.

Ride-on lawn mowers take the same types of oil, but it’s important to read your owner’s manual carefully. Most Briggs & Stratton engines are fine to be used with 10W-30, 5W-30, or SAE 30, based on the operating temperatures you’re likely to experience, but if your ride-on mower’s engine is produced by a different company, they may have a more specific recommendation.

How much oil to use

Man checking the oil level in his lawn mower.

Typically, most rotary lawn mowers will take about 20 ounces of oil from empty. Ride on mowers will take about 50-60 ounces of oil to fill up.

When adding oil, it’s important to pour it in slowly, and give the oil time to settle. Then, check the oil level, to see if more oil needs to be added.

Remember to remove the dipstick, wipe it down with a cloth, and then reinsert it, when you first check your oil level. This helps you to get a more accurate reading.

Avoid overfilling your lawn mower with oil, as this can cause your engine to overheat, and even damage your engine. Doing this will also result in white smoke billowing out of your mower when you start it up.

How often to change lawn mower oil

You should change your lawn mower’s engine oil at least once a year, ideally in the spring, or every 50 hours of use – whichever comes first. This will increase the longevity of your lawn mower, and ensure that it continues to run at its best.

If you use a fully synthetic engine oil, you might be able to get away with leaving the job a bit longer, up to 75 hours, but you should always replace your oil at least once a year. If your owner’s manual recommends very short oil change intervals, such as every 20 hours or so, we wouldn’t recommend leaving it much longer than 30-35/

On the other hand, if you have quite an old lawn mower, and you find that your oil gets dirty quite quickly, you might want to replace the oil more often – every 30-40 hours of usage or so.

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